Receiving means



March 31, 1936.

R. w. GEORGE RECEIVING MEANS Filed April 27, 1953" 6 Shets-Sheet 1INVENTOR RALPH W. GEORGE ATTORNEY March 31, 1936. R. w. GEORGE RECEIVINGMEANS 6 Sheets-Sheet 2 Filed April 27, 1953 Z [7: If; [2

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INVENTOR RALPH w. GEORGE ATIV'ORNEY March 31, 1936. 4 R. w. GEORGE2,035,745

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INVENTOR RALPH W. GEORGE BY iY Q /W v ATTORNEY March 31, 1936. R. w.GEORGE- RECEIVING MEANS 6 Sheets-Sheet 6 Filed April 27, 1953 llllllllvIvvvvI' INVENTOR RALPH w. GEORGE 76% ATTORNEY Patented Mar. 31 1936UNITED STATES PATENT OFFICE Ralph W. George, Riverhead, N. Y., assignorto Radio Corporation of America, a corporation of Delaware ApplicationApril 27, 1933, Serial No. 668,232 19 Claims. (01. 250-20) Thisinvention relates to a receiver particular- 1y adapted to relay and/oramplify and/pr demodulate signal modulated carriers of the order of 70centimeters in wave length or 428 megacycles in frequency. The inventionis general, however. and is in no way limited to this definite value ofwave length. My receiver demodulates carriers modulated in any of theircharacteristics, as for example, frequency or amplitude, or bothsimultaneously. For example, to obtain secret signalling I may key atone (in code) giving fr modulation at the transmitter for dots.

uency d key another tone at the transmitter giving amplitude modulationfor dashes.

The receiver is of the superheterodyne type. The demodulator may utilizea standard first detector and oscillator or may use a self-oscillatingfirst detector of 70 centimeter waves.

Preferably the self-oscillating detector is of the Barkhausen typegiving an output intermediate frequency of, say, 5.0 megacycles plus andminus the modulation frequency. The intermediate frequency amplifier isdesigned to amplify the band of frequencies between 4.7 and 5.3megacycles, the total band being approximately 600 kilocycles wide.

When frequency modulation is to be demodulated the system is broadly ofthe artificial line type similar to that disclosed in United Statesapplication Serial No. 618,154, filed June 20, 1932, in which amplitudemodulation is eliminated from the output.

Provi-' sion is made whereby the system may also receive amplitudemodulated waves.

The present system includes numerous novel features. The presentreceiver includes a novel frequency.

Another feature of the present invention is in the intermediatefrequency transformers which are arranged to pass a frequency band 600kilocycles wide, permitting the use of grea ter frequency modulationwhich is desirable, especially in the event there is present 10 or 20kilocycles of spurious modulation. This intermedi ate frequencyamplifier passes a band of suificient width to make its use intelevision desirable.

The in- E S EB JUN 40 195i termediate frequency amplifier is coupled byone path which includes phase shifting means and phase reversal means tothe grids of a pair of detector tubes in phase opposition, and overanother path by way of a coupling tube cophasally 5 to the electricalcenter of the input circuit.

In a modification increased efficiency is obtained by coupling thecophasal signal to the cathodes of the two detector tubes by way of acapacitive coupling instead of to the center tap of the input circuit.

The latter novel feature is further modified by directly coupling theanode of a coupling tube cophasally to the cathodes of the pair ofrectifiers.

An advantage gained by the use'of my novel system in the reception ofultra high frequencies with frequency modulation is that the amplitudemodulation caused by mechanical vibration of a high frequencyoscillating detector is balanced out in the succeeding stages of thereceiver.

F urthermore, practice has taught me that the tube hiss originating inthe first detector, whether of the self-oscillating Barkhaus'en type, asshown, or of the non-oscillating Barkhausen type using a separateheterodyne oscillator, is largely of amplitude modulation and thus isbalanced out to an appreciable extent. It is also known that hisoriginating in tubes at lower frequencies is likewise composed ofappreciable amplitude modulation, however in the described receiven byfar the largest value of tube hiss comes from the first detector.

The novel features of my invention have been set forth in the claimsappended hereto, as required by law.

The nature of my invention and the mode of operation of the same will bebest understood by the following description and therefrom when read inconnection with the attached drawings, 0 in which:

Figure 1 is a circuit diagram of a receiving system of the beat notetype by means of which ultra short waves modulated in frequency or inamplitude may be received, amplified and demod- 5 ulated;

Figure 1a shows a detail of the circuit of Figure 1;

Figures 11:, 2 and 3 show modifications of certain portions of thesystem of Figure 1; r

Figures 4, 5, 6 and 7 are curves and vector diagrams which help toillustrate the operation of the system; while.

Figure 8 shows a modification of'a portion oi.

the circuit of Figure 1.

The Barkhausen self-oscillator first detector stage BO which producesthe intermediate frequency has been described in detail in myapplication Serial No. 587,109, filed January 16, 1932, Patent#2,011,942, August 20, 1935. This oscillating detector comprises a tube0 having its control grid and anode connected by way of blockingcondensers to an antenna system as shown. The tube II is of theBarkhausen type and when the grid and plate are coupled by tun-' ingcapacity TC, as shown, acts as a self-oscillating detector operating ata frequency determined in part by the capacity TC. when the anode andgrid are energized by sources of direct current as shown.

The intermediate frequency amplifier is composed of six intermediatestages IF including six transformers T to T5 inclusive, each enclosed ina separate shield S to S5 inclusive and connected in cascade by thetubes I, 2, 3, I, and 5. Each transformer is enclosed in a shield, asshown, and energizing leads include the necessary filtering chokes andby-passing condensers to shunt radio frequency currents around thesources for the plates, screen grids, and cathode leads.

The secondary winding of the final intermediate frequency transformer T5is connected, as shown, to the control grid of a tube 6 and also to thecontrol grid of a coupling tube Ill. The anode of the tube 6 is coupledby a capacity 20, as shown, to the electrical center of the inductance30 connected between the control grids of the tubes 8 and 9 in abalanced demodulator stage. The anode of the tube I0 is coupled by wayof a phase shifting line L1, C2, CB, L2 enclosed in shield S6 to thecontrol grid of a tube I. The anode of tube 1 is coupled by the primarywinding PW of a phase changing transformer PC in'shield S7 to theinductance 30 which may be considered the secondary of this transformer.The primary winding of each transformer described hereinbefore lsseparated by an electrostatic shield SS from the secondary winding. Allintermediate frequency transformers including the phase changingtransformer PC are identical in constants and tuning adjustment. Boththe primary and secondary windings have fairly high inductance, say, 35microhenrys each, to give as high an impedance as practical and thusincrease the gain. The windings and tuning condensers are dampedsufficiently with the resistance across them to flatten the double humpfrequency response characteristic obtained by closely couplingthe'primary and secondary, as shown in Figure 4. In Figure 5 I haveshown the overall frequency response of the intermediate frequencyamplifier stages and the phase changing transformer including theartificial line in shield Sc.

The phase shifting line or artificial line in shield 56 may include theessential elements as shown in Figure 1 or the elements as shown indetail in Figure 1a.

The phase shifting line is of conventional low pass filter design togive the desired phase shift of at the grids of the detector tubes 8 and9 with respect to the cophasal voltage applied through tube 6. The phaseshifting line consists essentially of the elements C1, L1, C2, L2, Caand the characteristic impedance R1. The condenser CB is an addedblocking condenser and the resistances R1 and R2 are respectively usedto supply grid current to the tube and plate current to tube III. Inorder to obtain maximum impedance, C1 is replaced by the capacity of theplate of tube l0 and the stray capacities of the leads to ground asshown in Fig. 1. Likewise, C3 is replaced by the capacity of the grid oftube 1 to ground and a small condenser in parallel as shown in Figure 1.C1 and C3 are shown in dotted lines to indicate this. In operation, thephase shifting line acts as a transmission line of fixed physicallength, and is designed to have an electrical length of one-quarter waveat 5 megacycles, thus giving a corresponding time delay of wavepropagation of 90 degrees from the plate of tube In to the grid oftube 1. It is well known that in this type of artificial line, phaseshift is proportional to frequency; thus, when the 5 megacycle carriervaries plus and minus 5% as it is modulated, the phase shift in thisline varies from 90 degrees by plus and minus 5% which amounts to plusand minus 4 /2 degrees. This phase shift with frequency is, in fact, anadvantage in this case as it is cumulative with that occurring in thephase changing transformer, thus giving slightly better sensitivity ofthe frequency modulation detector. Since, in the phase changingtransformer, the ideal condition of plus and minus 90 degrees phasechange with modulation is not realized, the additional plus and minus 4degrees is of some value. In practice, of course, the above statedvalues are not necessarily used. The phase changing transformer isessentially one section of a band pass filter with a flat frequencyresponse characteristic as shown in Figure 4. This characteristic isobtained by tuning the primary and secondary independently of each otherto 5 megacycles, then closely coupling the two tuned circuits to givethe necessary coupling coeflicient of approximately 12% and the additionof the damping resistances "which are approximately 30% higher in valuethan the characteristic impedance of the filter. The above procedure iscommon practice in dealing with such types of band pass filters. It iswell known that in a band pass filter embodying a fiat frequencyresponse characteristic there occurs a phase shift proportional tofrequency over the fiat part of the characteristic; at the lowerfrequency the phase shift is zero; at the mid-band frequency it is 90degrees; and at the higher frequency it is degrees. I have drawn abroken curve in Figure 4, showing approximately the phase shift withfrequency. It will be seen that the useful phase change is about plusand minus 70 degrees; hence, the additional cumulative phase shiftoccuring in the phase shifting line, previously mentioned.isadvantageous in securing maximum sensitivity to frequency modulation.This fact can be readily seen from the vector diagrams in Figure 7.

As has been stated before, the IF transformers are identical in alldetails with the phase changing transformer, with the exception of themidtap on the secondary of the latter, and it follows that there will bea similar phase shift with frequency in each; however, it can be easilyseen that this phase shift is of no consequence in the frequencydemodulation system which begins with the cophasal output of the IFamplifier to tubes 6 and I0.

The incoming signal modulated oscillations set up oscillations in theoscillating detector B0 and produce signal carrying oscillations of anintermediate frequency.

The band of signal carrying intermediate frequencies is passed throughthe intermediate frequency amplifier and fed cophasally to the grids ofthe tubes 6 and I0. Tube 6 feeds the grids of the detector tubes 8 and 9cophasally at the center tap on the grid coil through the capacitivelycoupled circuit in the plate circuit of tube 6. The impedance of theplate of tube 8 to ground, and its associated radio frequency circuit,is, in accordance with the present invention, made to be as purelycapacitive as possible, and still retain a reasonable .impedance toeffect a 90 degree phase shift from the grid voltage to the outputvoltage applied cophasally from the anode of 6 byway of capacity 20 tothe electrical center of the inductance 30 connected to the detectorgrids. This capacitive impedance serves also to eliminate possible phaseshift of the intermediate frequency due to frequency shift in thiscircuit. Tube Hi feeds an artificial line Ll, C1, L2, Ca which givesrelatively a 90 degree phase shift of the voltage of the oscillations atthe anode of tube 1 as compared to the voltage of the oscillations onthe grid of tube ill. The phase shifted oscillations in the output oftube I are fed into the phase changing transformer PC in shield S1. Thephase changing transformer produces approximately an additional 90degree phase shift in the voltages of the oscillations, which phaseshift is cumulative at the mid-band of the passed frequency. The resultis that the band of signal carrying oscillations is fed differentiallyto the grids of the detector tubes 8 and 9 and to said grids 90 degreesout of phase with respect to a component of the signal which is fedcophasally to the grids of said tubes. The plates of the detectors 8 and9 are connected in push-pull by transformer FT and jacks 22 forfrequency modulation detection and in parallel by transformer AT andjacks 24 for amplitude detection. Signals resulting from demodulation ofamplitude modulated signals will appear in a circuit connected with jack24 while signals resulting from frequency modulation will appear in acircuit connected to jack 22.

Jacks 2| and 3| are provided for the connection of pate current metersas shown. These meters are necessary'in adjusting the receiver and arean aid in tuning. The follow ng conditions can be obtained by their aid.The detector tubes 8 and 9 must be balanced and their bias properlyadjusted for ordinary bias detection; the cophasal and antiphasalsignals impressed on the grids of tubes 8 and 9 must be adjusted to beequal for maximum sensitivity to conform to Figure 7; and in tuning. theIF must be at the mid-bandfrequency which is indicated by equal platecurrents. as can be seen in Figure 6.

Actually, both demodulated amplitude ani frequency types of modulationappear in each plate circuit.

More in detai the operation of the device is as follows. Ultra highfrequency signal carrying oscillations are converted by the oscillatingdetector 8 in stage B to a high intermediate frequency. The intermediatefrequency produced in 0 is taken from the control grid side of theBarkhausen circuit by a lead 26 and fed through the primary winding ofthe first intermediate transformer T. The total capacities connectedbetween the grid and ground, including mainly the by-pass condenser 28between the plate and grid of the Barkhausen circuit, are so adjusted asto tune the intermediate frequency transformer primary to resonance'atthe intermediate frequency. Thus. the by-pass condenser 28 serves twoman purposes. It acts as a by-pass path in the Barkhausen oscillatingdetector circuit to shunt the high frequency oscillations in saidcircuit around the energy sources and serves also for tuning theintermediate frequency out- -put circuit, giving maxmum coupling betweenthe detector and the intermediate frequency amplifier at theintermediate frequency. Any slight variation in the capacity of theBarkhauscn tunng condenser necessary to tune the Barkhausen oscillatorhas a negligible effect on the total capacity which tunestheintermediate frequency output circuit. The signal carryingintermediate frequency band is-amplified in the intermediate frequencyamplifier and fed cophasally to the coupling tubes 6 and Ill. Since itis thought that the use of a definite frequency to illustrate theinvention will make the same more clear. it is assumed that theintermediate frequency is 5 megacycles plus and minus 300 kilocycles.Applicant is not, however, limited to such frequencies since obviouslyothers may be used. Tube 6 is coupled to the electrical center of theinductance 30 between the grids of the detector tubes 8 and 9, thusfeeding the detector grids cophasally with signal voltages substantially90 degrees out of phase with the signal voltages at the grids of tubes 6and I0. Tube l0 feeds through the artificial line or other phaseshifting circuit in Se, coupling tube 1 and the phase changingtransformer PC, the. grid eectrodes of the detectors 8 and 9differentially phased signal, the voltage of which is substant a ly 180degrees out of phase. and in phase. at

the mid-band frequency, with respect to the voltage of the signal at thegrid of tube I 0. These voltages fed to the grids of tubes 8 andIll-therefore are plus and minus 90 degrees out of phas with respect tothe voltage of the signal fed cophasally from 6 to the grids of 8 andI!) as shown by the vector in Figurefl. More in detail. if we considerthe various voltages applied to the grids of tubes 8 and 9 vectorally wewill have a resultant voltage E 8 and Eg9 on the grids when ED9=thedifferential'y phased component. E=the cophasal component, and 0, thephase. is less than 90 degrees. Thus, at the mid-band frequency, theplate currents of the two detector tubes are equal. However. when thefrequency increases to 5.3 megacycles (max'mum), the inherent phasechange with frequency change in the phase changing transformer gives aphase change of the differentially fed signal approaching 90 degrees asa satisfactory operating limit. in which case the phase of thedifferentially fed signal on the grid of tube 8 s almost in phase withthe cophasaly fed signal, as. shown in the second diagram of Figure '7,and the phase of the differentially fed signal on the grid of tube 9 isalmost 180 degrees out of phase with the cophasally fed signal. Theconditions are reversed when the signal frequency approaches 4.7megacycles. the lower frequency limit of the band. The resultingdifferential plate current characteristic is shown by the curve inFigure 6 and converts the frequency moduations into amplitude changeswhen utilized by the audio transformer connected in push-pull to theoutput electrodes of tubes 8 and 9. The operation of a balancedmodulation detector of this type has been explained in United Statesapplicaton Serial No. 618,154, filed June 20, 1932. A brief statement ofthe manner in which the frequency modulations are converted intoamplitude variations when taken with the vectors of Figure 7 and curveof Figure 6 should suffice here. frequency modulated waves are appliedco phasally and in phase opposition to the control grids of tubes 8 and9. Assume the frequency is constant and at the center of the band offrequencies passed by the intermediate frequency amplifiers I, 2, 3, 4 5and 8.

It can be shown vectorally, as illustrated in the first diagram ofFigure 7 that these differentially and cophasally applied potentialswill, when combined, produce a resultant voltage. on the gridsbf tubes 8and 8 which can be shown to be 90 degrees out of phase. These resultantvoltages will produce a steady fiow of current in the output circuits ofeach of tubes 8 and 9. Since the output circuits of tubes 8 and 9 areconnected in push-pull for frequency modulation, the energies from thetwo tubes add and produce a resultant energy characteristic of the sumof the energies.

Frequency modulation causes the plate currents of the two detector tubesto vary differentially and according to the frequency modulation; thisvariation is utilized by the push-pull transformer connection; amplitudemodulation appears equally in both tubes and thereby is cancelled in thepush-pull transformer connection.

Now assume that the frequency of the oscillations passed by theintermediate frequency amplifier increases due to frequency modulation.The voltages applied to the control grids of the tubes 8 and 9 by thecophasal connection and by the phase opposition coupling will beshifted, as indicated by the second vector diagram in Figure '7. Thevoltages applied in phase opposition will I still be 180 degrees out ofphase with respect to each other but will be shifted in the spectrumwith respect to the voltages applied by the oscillations in phaseopposition when the frequency of the waves was at the midpoint of theintermediate frequency amplifier, as illustrated in diagram No. l ofFigure 7. This shifting of the frequency will, as shown vectorally inthe second diagram of Figure 7, produce new resultants on the grids oftubes 8 and 9, respectively. These resultant voltages are of diflerentamplitude and cause anode currents of different amplitude to flow in theoutput circuits, as illustrated in the diagram of Figure 6. Theamplitude of the combined resultants in the output circuit, of course,changes.

In like manner it has been shown vectorally in Figure 7 anddiagrammatically in Figure 6 that if the frequency of the waves passedby the intermediate frequency amplifier shifts to a value below themidpoint of the intermediate frequency amplifier, a shift of the vectorsin an opposite direction will take place, This shift produces resultantsof different voltage on the control grids of tubes 8 and 9 and thereforecauses said tubes to pass different values of anode current. In theabove manner the frequency modulation of the high frequency carrier iscaused to produce amplitude variations in current characteristic of thesignal modulations.

In Figure 1!) I have shown a modified means for applying the cophasalsignals from the tube 6 to the detector. As shown the amplifiedoscillations may be applied from the output of tube 6 to a separateelement such as an extra control grid EG in each of the tubes instead ofto the cathodes or to the control grids fed by the phase changingtransformer. The advantage is obvious in view of the possible highercapacitive reactance of such separate grid elements.

The

Strand 60 of the detectors 8 and 9.

If the oscillations at intermediate frequency are applied by way of thecoupling tube 6 cophasally to the cathodes of the tubes 8 and 9increased efficiency is obtained.

An additional circuit by means of which the oscillations may be appliedcophasally to the oathodes is illustrated in Figure 2. In Figure 2 theelements shown may replace the intermediate frequency transformerenclosed in the shield S5 the coupling tube 6, the artificial lineenclosed in the shield St, the tube ill, the tube "I, and the phaseshifting transformer PC and the detector' tubes 8 and 9. In Figure 2 theanodes of the tubes have been shown as being coupled in pushpullrelation for the reception of frequency modulated waves. Obviously, Icontemplate a parallel connection of the anodes of these tubes toreceive amplitude modulated waves.

In Figure 3 I have shown a modified form of the circuit of Figure 2. Thecircuit of Figure 3 may replace the same elements which the circuit ofFigure 2 may replace, as set forth above.

Figures 2 and 3 show two circuit variations in the phase shiftingtransformer coupling tube 6 and balanced modulator detectors 8 and 9which do not change the fundamental principles of operation but improvethe coupling of the cophasally fed signal to the detector. The circuitof Figure 2 is the same as the corresponding portion of the circuit usedin the embodiment described in connectlon with Figure l with theexception that the cophasal signal is fed to the cathodes 50 and 60 ofthe detectors 8 and 9 instead of to the center tap on the inputinductance 30. This results in approximately 50 percent more cophasalvoltage impressed on the detector, and simplifies the practicalarrangement of the circuit as shown.

In Figure 3 Iv have shown adirect coupled arrangement for feeding thecophasal signal from the plate of the coupling tube 6 to the cathodes ofFigures 2 and 3 are otherwise similar to the corresponding parts ofFigure 1 except that in the circuit of Figure 3 the filament heatingleads include radio frequency chokes as shown, the purpose of which isto reduce the capacity between the tube elements and ground.

Apparent advantages are, simplification of the circuit, and maximumcophasal signal voltage on the cathodes 50 and 60 of the detectors 8 and9. A further refinement of the circuit of Figure 3, which would apply tothe circuit of Figure l, is shown in the use of chokes in each side ofthe filament or heater leads. This greatly reduces the capacity betweenthe cathode and ground and results in an increase in the capacitiveimpedance to ground of the cophasal coupling circuit which increases thecophasal signal voltage impressed on the cathodes.

It is also obvious that, in order to get the desired phase relationbetween the cophasal and differential phased signal at the detectors 8and 9, any method of phase shifting or phase adiustment that is knownand is suitable may be used. Such phase adjustment need not necessarilybe made in the portion of the circuit in which the artificial line isplaced, that is, in the unit enclosed in S6, but itvmay be placed in anyother part of the circuit to accomplish the desired phase adjustment,such as in the cophasal cou- The circuits It is further conceived thatunder some conditions the intermediate amplifier will not be needed andthe first detector can be coupled directly to the second detector by wayof the phase shifting circuits and coupling tubes as shown.

The manner in which the electrodes of the tubes used in the variouscircuits are energized will be obvious by inspection of the drawings andneeds no detailed description here. It might be noted, however, that itis desirable to include in the screen grid energizing leads, in certainof the control grid energizing leads, and in certain of the anodeenergizing leads, choking inductances and radio frequency by-passcondensers to prevent ultra high frequency oscillations dealt with inthe receiver and the high frequency oscillations dealt with in theintermediate frequency amplifier from reaching the energizing sourcesand reacting therein to produce unstable operation of the device. Eachelement of the receiver is, as shown, included in a separate groundedshield to electrically isolate the circuits of the several elements toprevent reaction therebetween. The transformer windings of the variousintermediate frequency transformers and of the phase changingtransformers are separated as shown by electrostatic shields SS, whichmay be of the type covered by United States application No. 598,731,filed November 3, 1922, matured into Patent #1,942,578, on January 9,1934.

.Where signals modulated in frequency by a keyed tone to produce oneelement of a signal and simultaneously modulated .in amplitude byanother keyed tone to produce another signal element for secrecypurposes, and transmitted, the receiver of Figure 1 may be modified inits circuits associated with the output electrodes of detectors 8 and 9as indicated in Figure 8. Amplitude modulated signal elements could beseparated out from the frequency modulated signal elements by theparallel transformers PT and appear in any indicating device pluggedinto jack 40. The elements represented by frequency modulated waves willbe separated out in transformer FT and appear in an indicating deviceplugged into jack 42.

Having thus described my invention and the operation thereof, what Iclaim is:

1. Means for receiving signal modulated oscillations of ultra highfrequency comprising, an oscillating detector having a frequencydetermining circuit connected between its control grid and anode, acapacity by-passing said frequency determining circuit, said by-passingcapacity tuning said circuit to the beat frequency produced in saidoscillating detector due to reaction between the signal wave andoscillations produced in said detector, an intermediate frequencyamplifier coupled to said by-passing capacity, rectifying means, and aplurality of paths coupled between said intermediate frequency amplifierand said rectifying means, one of said paths including phase shiftingmeans.

2. A circuit for receiving signal modulated oscillations of ultra highfrequency comprising, an oscillating triode having control grid, anodeand cathode, and a frequency determining circuit connected between itscontrol grid and anode and to said cathode, means for impressing asignal wave on said triode, a capacity by-passing said frequencydetermining circuit, said bypassing capacity tuning said circuit to thebeat frequency produced in said oscillating detector due to reactionbetween signal wave and oscillations produced in saiddetector, anintermediate frequency amplifier coupled to said lay-passing capacityand tuned to the beat frequency, detecting means, and a plurality ofpaths coupled between said intermediate frequency amplifier and saiddetecting means, one of said paths including phase shifting means andphase reversing means.

3. A circuit for demodulating modulated waves.

of constant amplitude including, an oscillating detector comprising, athermionic tube having its input and output electrodes coupled by afrequency determining circuit and to radiant energy absorbing means, anintermediate frequency amplifier, a capacitive coupling between saidamplifier and said oscillating detector, a pair of thermionic tubes eachhaving like input electrodes, a phase shifting circuit coupled to saidintermediate frequency amplifier on the one hand and to like inputelectrodes of said thermionic tubes on the other hand, and a couplingtube having its input electrodes coupled to said intermediate frequencyamplifier on the one hand and its output electrodes coupled to said likeinput electrodes in said pair of thermionic tubes on the other hand.

4. A circuit for demodulating ultra high frequency waves including anoscillating detector comprising, a thermionic tube having its input andoutput electrodes coupled by a frequency determining circuit and toradiant energy absorbingmeans, an intermediate frequency amplifier, acapacitive coupling between said amplifier and said demodulating means,a pair of thermionic tubes each having a control electrode and an outputelectrode, a phase shifting circuit coupled to said intermediatefrequency amplifier on the one hand and to a control electrode in eachof said thermionic tubes on the other hand, a coupling tube having itsinput electrodes coupled to said intermediate frequency on the one handand its output electrodes coupled to a control electrode in each tube ofsaid pair of thermionic tubes on the other hand, and circuits connectingthe output electrodes of said tubes either in parallel or in push-pull.

5. The method of demodulating frequency modulated high frequencyoscillatory energy which includes the steps of, reducing the frequencyof said modulated oscillatory energy, amplifying said oscillatory energyof reduced frequency, dividing said amplified oscillatory energy intotwo portions each of which portions includes energy of the mean carrierfrequency and side band frequencies, producing a phase shift in theoscillatory energy of one of said portions, said produced phase shiftbeing 90 for the oscillatory energy of said portion of the meanfrequency, producing a phase shift of the oscillatory energy in saidother portion, the phase shift produced in said last portion beingsubstantially a phasereversal of the oscillatory energy of said lastnamed portion of the mean frequency, and differentially combining saidlast named oscillatory energy with the oscillatory energy in said one ofsaid portions to produce a resultant.

6. The method of demodulating signal carrying ultra high frequencyoscillatory energy which includes the steps of beating said oscillatoryenergy with other oscillations to reduce the frequency of saidoscillatory energy, amplifying said oscillatory energy of said reducedfrequency, dividing said amplified oscillatory energy into two portions,producing a phase shift in one of said portions, said produced phaseshift being substantially 90 for the oscillatory energy of said portionof the mean frequency, producing a phase shift of the oscillatory energyin the other of said portions, the phase shift produced in said lastportion being substantially a phase reversal of the oscillatory energyof said last portion of the mean frequency, differentially combiningsaid last named phase reversed oscillatory energy portion with the phaseshifted oscillatory energy in said first one of said portions, anddemodulating the combined oscillatory energy.

'7. Frequency modulated oscillation demodulating means comprising, athermionic tube having an input circuit responsive to said oscillationsand an output circuit, a pair of thermionic detectors having inputelectrodes, a phase shifting circuit coupling the output circuit of saidfirst named tube in phase opposition to the input electrodes of saidthermionic detectors, 9. second'thermionic tube having an input circuitresponsive to said oscillations said second thermionic tube having-anoutput circuit, and a circuit coupling the output circuit of said secondnamed tube cophasally to the input electrodes of said detectors.

8. Signal demodulating means comprising, a source of signal modulatedoscillations, a pair of thermionic detector tubes each having an inputelectrode and an anode, circuits connecting the 'anode electrodes ofsaid tubes in push-pull relaelectrode and an output electrode, said tubehaving its input electrode coupled to said source of oscillations, meansfor coupling the output electrode of said last named tube differentiallyto the input electrodes of said detector tubes including, a phaseshifting circuit and a phase shifting transformer, an additionalthermionic tube having input and output electrodes, said additional tubehaving its input electrodes coupled to said source of oscillations, anda circuit coupling the output electrodes of said additional tube cophasally to the input electrodes of said detector tubes.

9. In a signal demodulating means to be used with a source of signalmodulated oscillations, a pair of thermionic detector tubes each havingan anode, a cathode and a control grid, a circuit connecting thecathodes and anodes of said tubes in push-pull relation, a thermioniccoupling tube having input electrodes and output electrodes, said tubehaving its input electrode coupled to said source of oscillations, meansfor vcoupling the output electrodes of said last named coupling tubedifferentially to the control grids of said detectors, said meansincluding a phase shifting circuit and a phase shifting transformer, anadditional thermionic coupling tube having input electrodes and outputelectrodes, a circuit coupling the input electrodes of said additionaltube to said source of oscillations, and a circuit coupling the outputelectrodes of said additional tube cophasally to the cathodes of saiddetector tubes.

10. An arrangement as recited in claim 9 in which the output electrodesof said additional source of signal modulated oscillations of constantamplitude, a pair of thermionic tubes each having an anode and a cathodeand a plurality of control grid electrodes, a reactance having oneterminal connected to a control grid in one of said tubes and the otherterminal c-onnected'to a control grid in the other of said tubes, acircuit connecting a point on said reactance to the cathodes of saidtubes, a circuit connected to said source and coupled to said rcactancefor applying signal modulated oscillations in phase opposition from saidsource to said control grids-by way of said reactance, a circuitconnecting another control grid in each tube together and to the tubecathodes by way of a common impedance, and a circuit connecting saidsource of signal modulated oscillations to said impedance for applyingsignal modulated oscillations cophasally to said other control grids insaid tubes.

13. Frequency modulated oscillation demodulating means comprising, athermionic tube having an input circuit responsive to said oscillations,said tube also having an output circuit, a pair of thermionic detectorseach having an input electrode, a phase shifting network comprisingseries inductances separated by a series capacity connected in theoutput circuit of said first named tube, means for coupling said phaseshifting network in phase opposition to the input electrodes of saidthermionic detectors, a second thermionic tube having an inputcircuitresponsive to said frequency modulated oscillations, said secondtube also having an output circuit, and a circuit coupled to the outputcircuit of said last named tube and to the input electrodes of saiddetector for applying said oscillations from the output circuit of saidlast named tube cophasally to the input electrodes of said detectors.

14. A circuit for demodulating ultra high fre quency waves modulated inamplitude and in fre- I said electrodes together and to said radiantenergy absorbing means, an intermediate frequency amplifier, capacitivemeans coupling said intermediate frequency amplifier to said oscillatingde tector, a pair of thermionic detector tubes having input electrodesand output electrodes, a phase shifting circuit coupled between saidintermediate frequency amplifier and the input electrodes of saidthermionic detectors, said phase shifting circuit including inductancesin series separated by a series capacity and a parallel capacity, acoupling tube having input electrodes and output electrodes, meanscoupling said input electrodes to said intermediate frequency amplifier,means coupling the output electrodes of said coupling tube to the inputelectrodes of said pair of thermionic tubes, a plurality oftransformers, one of said transformers having a single primary windingand the other of said transformers having a pair of primary windings,circuits connecting the output electrodes of said tubes in push-pullrela- "ill tion through the primary winding of said transformer having asingle primary winding, circuits connecting the output electrodes ofsaid tubes in parallel through the primary windings of said transformerhaving a pair of primary windings, and means for connecting means withthe secondary windings of each of said transformers.

15. A device for converting signal modulated oscillations of an ultrahigh frequency into characteristic signal modulated oscillations oflesser frequency comprising, an electron discharge device having ananode, a cathode and a control electrode, a conductor connected to thecontrol electrode of said tube, a conductor connected to the anode ofsaid tube, a circuit for maintaining the control electrode of said tubeat a high positive potential with respect to the anode and cathode ofsaid tube whereby oscillations are produced in said tube, a condenserconnected between said conductors to tune the circuit formed by saidconductors and said condenser to a frequency equal to the frequency of'the signal wave plus or minus the frequency to which it is desired toconvert the signal carrying ultra high frequency oscillations, a circuitfor impressing the ultra high frequency signal modulated wave on saidconductors, and a second condenser connected across said conductors atpoints spaced from said first named condenser, said second namedcondenser serving to tune the circuit formed thereby and by the othercondenser and conductors to the lower frequency desired, to by-pess theultra high frequency oscillations and to couple said circuit to a load.

16. In combination in an ultra high frequency wave receiving system, abipolar antenna tuned to the incoming signal wave, an ultra highfrequency oscillating demodulator of the beat frequency type forproducing an intermediate frequency, said oscillator comprising, anelectron discharge device having an anode, a control electrode and acathode, and having means for maintaining the control electrode at ahigh positive potential relative to the cathode and anode, a pair ofLecher wires conected to said'anode and control electrode, a tuningcondenser connected across said Lecher wires, said antenna being coupledto said Lecher wires through blocking condensers, an additionalcondenser connected across said Lecher wires, said additional condenseracting as a by-pass for the ultra high frequency oscillations and totune said Lecher wires to the intermediate frequency and an outputcircuit cou- Died to said Lecher wires.

17. A circuit for demodulating ultra high frequency waves modulated inamplitude and in frequency including an oscillating detector comprising,radiant energy absorbing means, a thermionic tube having input andoutput electrodes, said input and output electrodes being coupledtogether by a frequency determining circuit and connected to saidradiant energy absorbing means, an intermediate frequency amplifier,capacitive means coupling said intermediate frequency amplifier to saidoscillating detector, a

pair of thermionic detector tubes each having a controlling electrodeand an anode, a phase shifting circuit coupled to said intermediatefrequency amplifier on the one hand and to a controlling electrode ineach of said thermionic detectors on the other hand, said phase shiftingcircuit including inductances in series and a parallel capacity, acoupling tube having input electrodes and output electrodes, meanscoupling said input electrodes to said intermediate frequency amplifierand said output electrodes to a controlling electrode in each tube ofsaid pair of thermionic tubes, a plurality of transformers each having aprimary winding and a secondary winding, a circuit connecting the anodesof said pair of tubes in pushpull relation through the primary of one ofsaid transformers, circuits connecting the anodes of said pair of tubesin parallel through the primary winding of the other of saidtransformers, and means for connecting an indicator with the secondarywinding of each of said transformers.

18. The method of demodulating ultra high frequency oscillatory energywhich has been modulated in frequency in accordance with signals whichincludes the stepspf reducing the fre quency of said oscillatory energywithout reducing the degree of modulation thereon, dividing saidoscillatory energy into two portions, producing a phase shift in theenergy of one of said portions such that there is a phase quadraturerelation between the energies in said respective portions, anddifferentially combining the energies to render the signal.

19. In a signal demodulating system to be used with a source of signalmodulated oscillations, a pair of thermionic detector tubes each havinga control grid, a cathode and an anode, output circuits connected withthe anodes of said tubes, a thermioniccoupling tube having input andoutput electrodes, a circuit connecting the input electrodes of saidcoupling tubes to said source of signal modulated oscillations, areactance connectingthe control grids and cathodes of each of saiddetector tubes in parallel, a circuit coupling the output electrode ofsaid coupling tube to said reactance, said last named circuit includingphase shifting means, an additional coupling tube having inputelectrodes and output electrodes, a circuit connected with the inputelectrodes of said additional coupling tube, said circuit being coupledto said source of signal modulated oscillations, a phase shiftingcircuit comprising series inductances and parallel capacitancesconnected between the output electrodes of said additional couplingtube, a third coupling tube having input and output electrodes, acircuit connecting the input electrodes of said third coupling tube tosaid phase shifting circuit, and a transformer having a primary windingcoupled to the output electrodes of said third coupling tube, and asecondary winding connected

